Sajid Aleem Khan

Biochemical alterations in leaves of resistant and susceptible cotton genotypes infected systemically by cotton leaf curl Burewala virus

Leaf curl disease caused by Cotton Leaf Curl Burewala virus (CLCuBuV) has been recognized as serious threat to cotton in Indian subcontinent. However, information about cotton–CLCuBuV interaction is still limited. In this study, the level of phenolic compounds, total soluble proteins, and malondialdehyde (MDA) and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POX), catalase (CAT), proteases, superoxide dismutase (SOD), and polyphenol oxidase (PPO) were studied in leaves of two susceptible (CIM-496 & NIAB-111) and two resistant (Ravi and Co Tiep Khac) cotton genotypes. Disease symptoms were mild in the resistant genotypes but were severe in highly susceptible genotypes. The results showed that phenolic compounds, proteins, PAL, POX, CAT, proteases, SOD, PPO, and MDA play an active role in disease resistance against CLCuBuV. The amount of total phenols, proteases, MDA, and PPO was significantly higher in leaves of CLCuBuV-inoculated plants of both resistant genotypes as in non-inoculated plants, and decreased in CLCuBuV-inoculated plants of both susceptible genotypes over their healthy plants. POX, protein content, SOD, and PAL activities showed lower values in resistant genotypes, while they decreased significantly in susceptible genotypes as compared to the noninoculated plants except PAL, which showed non-significant decrease. CAT was found to be increased in both susceptible and resistant genotypes with maximum percent increase in resistant genotype Ravi, as compared to non-inoculated plants. The results showed significantly higher concentrations of total phenols and higher activity of protease, MDA, SOD, and PPO in resistant genotype Ravi after infection with CLCuBuV, suggesting that there is a correlation between constitutive induced levels of these enzymes and plant resistance that could be considered as biochemical markers for studying plant-virus compatible and incompatible interactions.

Transgenic expression of antifungal pathogenesis-related proteins against phytopathogenic fungi – 15 years of success

ABSTRACTBeing sessile organisms, plants are continuously challenged by phytopathogenic fungi, contributing the largest share in loss due to plant disease. Plants naturally possess a well-developed and programmed protein-based defense system, capable of producing antimicrobial cationic peptides to ward off pathogen attack. Numerous genes encoding antifungal proteins have been isolated, cloned, sequenced and transgenically expressed against multiple phytopathogenic fungi successfully. Genetic engineering technology has been widely utilized to produce transgenic plants with enhanced resistance against pathogens. Pathogenesis-related proteins (PR-proteins) is a group of the most important inducible defense-related antifungal proteins, including defensins, thionins, osomtin-like proteins, thaumatin-like proteins, chitinases, glucanases, oxalate oxidase or oxalate oxidase-like proteins and lipid transfer proteins. Transgenic plants have been developed by imparting the artificial expression of genes encoding ant...

Bio-management of tomato wilt complex caused by Meloidogyne incognita and Fusarium oxysporum f. sp. lycopersici

The potential of biocontrol agents Purpureocillium lilacinum (Paecilomyces lilacinus) and Trichoderma harzianum was evaluated against tomato wilt complex, caused by a combination of Meloidogyne incognita and Fusarium oxysporum f. sp. lycopersici, under both laboratory and field conditions. Biocontrol agents at spore concentration of 1 × 106 spores ml−1 were applied alone and in combined treatments. The results of combined application revealed maximum mortality and inhibition of hatching of M. incognita under in vitro conditions. Combined application of both antagonistic fungi was found to be more effective in mycelial inhibition of Fusarium oxysporum f. sp. lycopersici. In glasshouse trials, application of T. harzianum promoted overall plant growth, followed by combined application of P. lilacinum and T. harzianum; nematode development parameters and fungus damage were significantly reduced. Under field conditions, the combined application of P. lilacinum and T. harzianum increased the number of leaves, shoot length, shoot weight and root length, and decreased root weight, with minimum number of females and egg masses of M. incognita per root system and mycelia inhibition of F. oxysporum.

EFFICACY OF RHIZOSPHERIC ORGANISM Rhizobium leguminosarum AGAINST Meloidogyne incognita IN SOYBEAN

Present investigation was carried out to assess the biocontrol potential of Rhizobium leguminosarum against root-knot nematode, Meloidogyne incognita on soybean. Effect of Rhizobium strains LSI-21 and CRI-29 was assessed individually and concomitantly on reproduction of M. incognita. In vitro studies were conducted to check the effect of Rhizobium strains on egg hatching and juvenile mortality of M. incognita. Concomitant application of Rhizobium strains was more effective in reducing egg hatching and causing juvenile mortality as compared to individual treatment. In green house, Rhizobium strains were used as soil drench and seed dressing for the management of root knot nematode on soybean. It caused considerable reduction in reproduction of root knot nematode as well as improved plant growth parameters of soybean. Seed dressing showed most significant results than soil drenching. It is interesting to note that Rhizobia not only controlled reproduction of M. incognita but also an increase in plant height, fresh and dry root shoot weight was observed. It would seem that Rhizobium being a good rhizosphere organism for field and vegetable crops presumably prevent the contact of pathogenic organisms on roots.

An LRR receptor kinase regulates growth, development and pathogenesis in Phytophthora capsici

Leucine-rich repeats (LRRs) domain containing kinase proteins (LRR-RK) perform various functions in eukaryotic organisms. However, their functions in Oomycetes are still largely unknown. Here, we identified an LRR-RK (PcLRR-RK1) gene and characterized its functions in Phytophthora capsici, a model oomycete specie and a major plant destroyer of solanaceous and cucurbitaceous vegetable crops. We showed that PcLRR-RK1-silenced P. capsici transformants exhibited reduced growth and produced highly branched fluffy hyphae. The shape and size of sporangia were also altered along with the reduced production of number of sporangia and zoospores. Moreover, silencing of the gene affected the cyst germination and penetration of germ tube into the host tissues, and led to the reduced virulence of P. capsici. Thus, we suggest that PcLRR-RK1 was essentially required for zoospores development, and successful infection of the P. capsici.

Exploitation of Nematicidal Potential of Paecilomyces lilacinus against Root Knot Nematode on Eggplant

ABSTRACT Root knot nematodes cause severe losses in vegetables throughout the world because its management is difficult due to its wide host range. The nematicidal potential of Paecilomyces lilacinus (Thom.) Samson was evaluated against root knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, on eggplant (Solanum melongena L.) under greenhouse conditions. Inoculation with M. incognita and P. lilacinus was carried out individually, in combination, and sequentially. Inoculation of 1000 juveniles (J2) of M. incognita reduced plant growth. The sequential application of P. lilacinus 7 days prior to M. incognita was more effectual than sequential application of M. incognita 7 days prior to P. lilacinus. Our findings concluded that P. lilacinus has the aptitude to adjust the nematode population and may serve as an alternative to nematicide.

Efficacy of Biopesticides for Management of Root Knot Nematode on Tomato

Biopesticides are being tested in control parasitic nematodes as a replacement for synthetic chemicals. This study was undertaken to investigate effects of the biopesticides abamectin, emamectin, and biosal on egg hatch and mortality of second instar juveniles (J2) of Meloidogyne incognita (Kofoid and White) Chitwood under laboratory and field conditions on tomato (Solanum lycopersicum L). Treatments consisted of the biopesticides and water (control). Numbers of J2 hatched was determined at 1, 3, and 6 days and mortality of J2 at 12, 24, and 48 h after inoculation. Evaluation of biopesticides under field conditions was for yield, number of flowers, numbers of fruit per plant, average fruit weight, shoot and root length, numbers of galls and egg masses per root system, and nematode rate of reproduction. Abamectin was more effective than emamectin and biosal against M. incognita under laboratory and field conditions. Application of abamectin produced the highest juvenile mortality and increased fruit weight, reduction in egg hatch, gall number, egg mass number, and rate of reproduction. Abamectin can be used under field conditions for management of M. incognita.

Evaluation of persistence and effectiveness of bacterial cell suspensions and culture filtrates against M. incognita on brinjal

Keeping in view the staid health and ecological apprehensions coupled with the use of pesticides, entomopathogenic nematodes have the potential to supersede pesticides for the management of various pests. Brinjal plants are the most seriously affected by Meloidogyne incognita. The main objective of this study was to evaluate the persistence effectiveness of bacterial cell suspensions (Xenorhabdus and Photorhabdus spp.) and their culture filtrates in soil up to 7, 14 and 21 days and their response against M. incognita as a source of biological control for nematode management. In a life cycle study, Xenorhabdus and Photorhabdus spp., isolated from Steinernema asiaticum and Heterorhabditis bacteriophora, were proved more effective in influencing the life cycle of RKNs. It was found that all the treatments of bacterial cell suspensions and their culture filtrates at all persistent times proved effective in reducing the number of females and egg masses as compared to control. It delayed penetration of nematode juveniles (J2) into host roots. It was concluded that persistence effectiveness of bacteria and their metabolites decreased in soil with time.